A binoculars is generally formed of a frame, two cylindrical bodies, and a focusing device. The cylindrical bodies are rotatably held by the frame and are provided therein with an objective lens set, a prism set, and an eyepiece set. The frame is provided with a receiving space in which a focusing device is disposed such that the focusing device is linked with the objective lens set. The eye range, which is the distance between the central axes of the two ocular lenses, is adjusted by swiveling the two cylindrical bodies. Such conventional method and device as described above should be revolutionized.